Those who are interested in the design of constant impedance amplitude equalizers
can download the file <Bridged-T Amplitude Equalizers.zip> with eight different implementations

(from type I to type VIII), with lowpass, highpass, bandpass and bandreject responses.

See the Temp folder: https://groups.io/g/LTspice/files/Temp?p=created,,,50,2,0,0

 

Types I to IV are the simplest ones, with unlimited maximum insertion loss, while Types V to VIII 
pose a limit to the maximum insertion loss. The component values are calculated with the formulae described in the

second edition of the Electronics Designer's Handbook by L.J. Giacoletto, pages 7-5 to 7-8.

 

The results appear on the schematic pages following Andy's example
in https://groups.io/g/LTspice/files/z_yahoo/Files%20sorted%20by%20message%20number/msg_126391//Par_Values_on_Schematic_AI.asc
and as further explained in: https://groups.io/g/LTspice/topic/showing_calculated_parameters/109650378

 

The input parameters are:

 

- The characteristic impedance of the network (Ro) in Ohms, for all equalizers.
- The 3 dB insertion loss frequency (f3dB) in MHz, for Types I to IV.
- The maximum insertion loss (Loss) in dB, for Types V to VIII.
- The frequency (fb) at 1/2 maximum insertion loss (in dB), for Types V to VIII. 
- The resonant frequency (fres) in MHz, for Types III, IV and VII, VIII. 
  (Note: fres>f3db and>fb)

 

The frequency response traces are displayed as V(out)/V(in).